From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754622AbaE1Iqz (ORCPT ); Wed, 28 May 2014 04:46:55 -0400 Received: from mx0.aculab.com ([213.249.233.131]:40655 "HELO mx0.aculab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751984AbaE1Iqx (ORCPT ); Wed, 28 May 2014 04:46:53 -0400 From: David Laight To: "'Cody P Schafer'" , LKML , Linux PPC CC: Sukadev Bhattiprolu Subject: RE: [PATCH 11/16] byteorder: provide a linux/byteorder.h with {be, le}_to_cpu() and cpu_to_{be, le}() macros Thread-Topic: [PATCH 11/16] byteorder: provide a linux/byteorder.h with {be, le}_to_cpu() and cpu_to_{be, le}() macros Thread-Index: AQHPehtRSTTppVgBd0OVC+FRTYrw6JtVrLPQ Date: Wed, 28 May 2014 08:45:52 +0000 Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1724EEAF@AcuExch.aculab.com> References: <1401236684-10579-1-git-send-email-dev@codyps.com> <1401236684-10579-12-git-send-email-dev@codyps.com> In-Reply-To: <1401236684-10579-12-git-send-email-dev@codyps.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.202.99.200] Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id s4S8l5Xw029308 From: Cody P Schafer > Rather manually specifying the size of the integer to be converted, key > off of the type size. Reduces duplicate size info and the occurance of > certain types of bugs (using the wrong sized conversion). ... > +#define be_to_cpu(v) \ > + __builtin_choose_expr(sizeof(v) == sizeof(uint8_t) , v, \ > + __builtin_choose_expr(sizeof(v) == sizeof(uint16_t), be16_to_cpu(v), \ > + __builtin_choose_expr(sizeof(v) == sizeof(uint32_t), be32_to_cpu(v), \ > + __builtin_choose_expr(sizeof(v) == sizeof(uint64_t), be64_to_cpu(v), \ > + (void)0)))) ... I'm not at all sure that using the 'size' of the constant will reduce the number of bugs - it just introduces a whole new category of bugs. Using the size of the destination might help, but that makes the code ugly. Getting one of the static analysers to find the obvious errors is probably more appropriate. David {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I